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Sprint's new half-off promotion may sound pretty great, but there's a catch. Once you factor in the cost of paying for your new smartphone, most people will only see their monthly bill drop by about 20-percent.

CFO Joe Euteneuer revealed the truth behind the carrier's latest promotion on Tuesday while speaking at a Merrill Lynch conference, Re/code reports. "They are still probably getting a 20-percent sort of net discount," he said, adding that some of Sprints current plans may actually be even cheaper than what's available through the company's latest promotion.

In case you missed it, Sprint is basically promising to cut what you currently pay with AT&T and Verizon in half when you switch. The carrier is also offering $350 to pay off any early termination fees you might incur. It's still a pretty nice deal, but we can't help but feel like we've been tricked.

Euteneuer also responded to a question asking why Sprint wasn't going after T-Mobile customers with its latest promotion, explaining that there are simply more people who might switch from one of the bigger carriers. T-Mobile has offered similar promotions in the past, though the UnCarrier's never been afraid to go after Sprint's customer base as well.